Markers
A Y-DNA test ranges from 10 to 111 markers on the Y chromosome. Most surname projects suggest at least 25 markers. Test results tell how many repeats a given subject has at a particular marker; the variations of repeats are known as alleles. For example, at DYS455, the results will normally show 8, 9, 10, 11, or 12 repeats. The specific test results for a given individual are referred to as a haplotype. When a surname project has enough participants' test results, it can group similar test results together and determine a modal haplotype for each such group of similar test results.
Read more about this topic: Surname DNA Project